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.Dd April 19, 2022
.Dt DRIVER_MODULE 9
.Os
.Sh NAME
.Nm DRIVER_MODULE ,
.Nm DRIVER_MODULE_ORDERED ,
.Nm EARLY_DRIVER_MODULE ,
.Nm EARLY_DRIVER_MODULE_ORDERED
.Nd kernel driver declaration macro
.Sh SYNOPSIS
.In sys/param.h
.In sys/kernel.h
.In sys/bus.h
.In sys/module.h
.Fn DRIVER_MODULE name busname "driver_t driver" "modeventhand_t evh" "void *arg"
.Fn DRIVER_MODULE_ORDERED name busname "driver_t driver" "modeventhand_t evh" "void *arg" "int order"
.Fn EARLY_DRIVER_MODULE name busname "driver_t driver" "modeventhand_t evh" "void *arg" "int pass"
.Fn EARLY_DRIVER_MODULE_ORDERED name busname "driver_t driver" "modeventhand_t evh" "void *arg" "enum sysinit_elem_order order" "int pass"
.Sh DESCRIPTION
The
.Fn DRIVER_MODULE
macro declares a kernel driver.
.Fn DRIVER_MODULE
expands to the real driver declaration, where the phrase
.Fa name
is used as the naming prefix for the driver and its functions.
Note that it is supplied as plain text, and not a
.Li char
or
.Li char * .
.Pp
.Fa busname
is the parent bus of the driver (PCI, ISA, PPBUS and others), e.g.\&
.Ql pci ,
.Ql isa ,
or
.Ql ppbus .
.Pp
The identifier used in
.Fn DRIVER_MODULE
can be different from the driver name.
Also, the same driver identifier can exist on different buses,
which is a pretty clean way of making front ends for different cards
using the same driver on the same or different buses.
For example, the following is allowed:
.Pp
.Fn DRIVER_MODULE foo isa foo_driver NULL NULL ;
.Pp
.Fn DRIVER_MODULE foo pci foo_driver NULL NULL ;
.Pp
.Fa driver
is the driver of type
.Li driver_t ,
which contains the information about the driver and is therefore one of the
two most important parts of the call to
.Fn DRIVER_MODULE .
.Pp
The
.Fa evh
argument is the event handler which is called when the driver (or module)
is loaded or unloaded (see
.Xr module 9 ) .
.Pp
The
.Fa arg
is unused at this time and should be a
.Dv NULL
pointer.
.Pp
The
.Fn DRIVER_MODULE_ORDERED
macro allows a driver to be registered in a specific order.
This can be useful if a single kernel module contains multiple drivers
that are inter-dependent.
The
.Fa order
argument should be one of the
.Xr SYSINIT 9
initialization ordering constants
.Pq Dv SI_ORDER_* .
The default order for a driver module is
.Dv SI_ORDER_MIDDLE .
Typically a module will specify an order of
.Dv SI_ORDER_ANY
for a single driver to ensure it is registered last.
.Pp
The
.Fn EARLY_DRIVER_MODULE
macro allows a driver to be registered for a specific pass level.
The boot time probe and attach process makes multiple passes over the
device tree.
Certain critical drivers that provide basic services needed by other
devices are attached during earlier passes.
Most drivers are attached in a final general pass.
A driver that attaches during an early pass must register for a specific
pass level
.Pq BUS_PASS_*
via the
.Fa pass
argument.
Once a driver is registered it is available to attach to devices for
all subsequent passes.
.Pp
The
.Fn EARLY_DRIVER_MODULE_ORDERED
macro allows a driver to be registered both in a specific order and
for a specific pass level.
.Sh SEE ALSO
.Xr device 9 ,
.Xr driver 9 ,
.Xr module 9 ,
.Xr MODULE_PNP_INFO 9 ,
.Xr SYSINIT 9
.Sh HISTORY
Prior to
.Fx 14.0 ,
these macros accepted an additional
.Vt devclass_t
argument after
.Fa driver .
.Sh AUTHORS
This manual page was written by
.An Alexander Langer Aq Mt alex@FreeBSD.org .
